It’s no mystery that demand across the grid fluctuates constantly. Time of day, the changing seasons, new technologies — all these variables alter grid loading. To meet the ups and downs, generation plants must be able to maintain a certain voltage level to provide constant, reliable power to customers and avoid potential violations of the North American Electric Reliability Corporation (NERC) VAR-002 standard.

In simple terms, part of the NERC VAR-002 standard requires generator operators to maintain output voltage levels within set parameters. This means that generator operators must keep a keen eye on bus voltage and adjust generator excitation multiple times throughout their shift.

Human error, unfortunately, can result in potential violations. A trend in the power industry is that operators are often being asked to do more with less. Certain software logic — implemented into the distributed control system (DCS) at a generation plant — can further automate the voltage regulation process, giving operators the ability to respond to other plant needs while avoiding potential NERC violations.

How It Works

This upgrade is possible if a generator’s automatic voltage regulator (AVR) can be controlled via the DCS.

First, the voltage master sends a signal to each generator’s unit voltage master, telling it to provide a certain amount of reactive power output. The unit voltage master will then pulse each generator’s AVR to achieve the desired reactive power output. Using the received bus voltage feedback, the voltage master will continue to send the unit voltage master a reactive power output setpoint as necessary to maintain the NERC VAR-002 schedule. This process can be applied to a single generator feeding a high-voltage bus or multiple generators in parallel feeding a single high-voltage bus.

This new logic can also be designed to generate a signal within the DCS that then sends at automatic alarm to transmission operations alerting them to the plant’s status, if required.

Why It Matters

With this logic solution, operators will not be required to manually adjust voltage throughout the day, further improving overall plant operations while avoiding potential regulation violations and providing reliable power to customers. Plus, even if a plant doesn’t have a previous violation and understands the risks involved, this solution still allows operators to remove some manual work from their plates and focus on making other areas of plant operation more efficient.

Our engineers' operational experience has proven first-hand the value offered by this logic addition and can provide plant operator training after implementation.

 

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by
Tommy Della Rocco is an electrical engineer at Burns & McDonnell. As a former U.S. Navy nuclear surface warfare officer, he uses his experience in the hands-on maintenance and operation of electrical plants to assist power plant clients in maintaining peak efficiency, adhering to regulations and solving other complex issues.